Vizio V755-J04 no backlight

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  • Lee M.
    Member
    • Nov 2021
    • 35
    • United States

    #1

    Vizio V755-J04 no backlight

    When set is plugged in the BL will flash on for 1/2 sec and show the Vizio logo. I can shine a flashlight on the screen and still see the logo. Checking voltages on the PS/BL driver board look good on the connector to the main board with 5V on pin 15 (BL on/off). The voltage on the two BL connectors jump to around 90V for 1/2 sec when the AC power cord is plugged in then drop to .6V. I tried it with BL's connected and with BL's disconnected and the voltage was the same, jump to around 90V and then drop to around .6V. If the PS/BL driver board is good shouldn't the voltage stay up around 90V and not drop like this board is doing? thanks, Lee
  • nomoresonys
    Badcaps Legend
    • Jan 2013
    • 12097
    • U.S.

    #2
    Re: Vizio V755-J04 no backlight

    need good pictures of each board and one of the whole back as to see how everything is connected.

    Comment

    • diif
      Badcaps Legend
      • Feb 2014
      • 6978
      • England

      #3
      Re: Vizio V755-J04 no backlight

      The voltage drops as it's detecting a problem with the LEDs or wiring, probably the LEDs.

      Comment

      • Lee M.
        Member
        • Nov 2021
        • 35
        • United States

        #4
        Re: Vizio V755-J04 no backlight

        If there is one or more shorted LED's the amp draw would be high and the protection circuit would shut down the BL's. But if I disconnect the BL's so there is no load it does the same exact thing, 90V for 1/2 sec and then nothing. It seems like I remember testing other BL driver boards and when I disconnected the BL's the voltage on the connector pins would stay up and not drop to zero with no load like this one is doing. That is how I knew the BL's were bad and not the driver board. Since this one is acting the same regardless if the BL's are connected or not has me wondering if the driver board might be bad?

        Comment

        • Lee M.
          Member
          • Nov 2021
          • 35
          • United States

          #5
          Re: Vizio V755-J04 no backlight

          vizio e650i-a2 backlight flashes then turns off
          vizio e650i-a2 (LWJAOZBP Serial) led backlight flashes then turns off, has video (via flashlight) and audio.

          panel: au optronics T650HVN05.4
          72 led total on 12 strips, 6 led per strip wired in three groups of 24 (led driver board has three anode and three cathode pins)
          link to datasheet: https://datasheetspdf.com/pdf-file/8.../T650HVN05.4/1

          Vizio 56.04219.641G (liteon PA-3231-01WN-LF) Power Supply Unit
          https://www.shopjimmy.com/vizio-56-0...-power-supply/

          Vizio 55.75J01.001G (91.75J10.004G) Main Board
          https://www.shopjimmy.com/vizio-55-7...-for-e650i-a2/

          Vizio 55.65T07.C07 (T650HVJ02.0, 65T09-C00) T-Con Board
          https://www.shopjimmy.com/vizio-55-6...oard-e650i-a2/

          Vizio 55.64S03.DE0 (4H+V3516.001/D) LED Driver Board
          https://www.shopjimmy.com/vizio-55-6...-for-e650i-a2/

          Vizio T650HVN05.4 LED Backlight Strips
          vizio ep-65t01e01-jaa4x 65" led light bar
          https://www.shopjimmy.com/vizio-t650...ght-strips-12/

          voltages with tv off and plugged in:
          ====================================
          Power Supply
          cn203 (12 pins)
          pins 1-5 (vddb)= 0v
          pins 6-10 (blgnd)
          pins 11-12= N/C

          cn202 (14 pins)
          pins 1-5 (vddb)= 0v
          pins 6-10 (blgnd)
          pin 11 (lamp_det)= 0v
          pin 12 (vblon)= 0v
          pin 13= N/C
          pin 14 (dim)= 0v

          cn201 (4 pins)
          pins 1-2 (24v)= 0v
          pins 3-4 (gnd is marked on board, but pin 3 is N/C)

          cn101 (15 pins)
          pins 1-2 (5vsb marked on board, but pin 2 is N/C)= 5.04v
          pin 3 (ac_off_det)= .655v
          pin 4 (ps_on)= 66mv
          pins 5-6 (gnd)
          pins 7-8 (5vres marked on board, but no pins connected)
          pins 9-10 (gnd marked on board, but pin 10 is N/C)
          pins 11-12 (reg_12v)= 0v
          pin 13 (vblon)= 0v
          pin 14 (dim)= 0v
          pin 15 (lamp_det marked on board, but pin is N/C)

          led driver board:
          cn1 (14 pins)
          pins 1-5 (vddb)= 0v
          pins 6-10 (blgnd)
          pin 11 (det)= 0v
          pin 12 (vblon)= 0v
          pin 13 (N/C)
          pin 14 (e_pwm)= 0v

          cn2 (12 pins)
          pins 1-5 (vddb)= 0v
          pins 6-10 (blgnd)
          pins 11-12 (N/C)

          cn3 (12 pins to led strips, only uses six wires)
          pin 1 (1anode)= 0v
          pins 2-3 (N/C)
          pin 4 (2cathode)= didn't measure this pin
          pin 5 (3anode)= 0v
          pins 6-7 (N/C)
          pin 8 (4cathode)= didn't measure this pin
          pin 9 (5anode)= 0v
          pin 10-11 (N/C)
          pin 12 (6cathode)= didn't measure this pin
          ================================================== ======

          voltages with tv on:
          ====================
          Power Supply
          cn203 (12 pins)
          pins 1-5 (vddb)= 24.68v
          pins 6-10 (blgnd)
          pins 11-12= N/C

          cn202 (14 pins)
          pins 1-5 (vddb)= 24.70v
          pins 6-10 (blgnd)
          pin 11 (lamp_det)= 0v
          pin 12 (vblon)= 3.3v
          pin 13= N/C
          pin 14 (dim)= 2.278v

          cn201 (4 pins)
          pins 1-2 (24v)= 24.70v
          pins 3-4 (gnd is marked on board, but pin 3 is N/C)

          cn101 (15 pins)
          pins 1-2 (5vsb marked on board, but pin 2 is N/C)= 5.03v
          pin 3 (ac_off_det)= .649v
          pin 4 (ps_on)= 2.368v
          pins 5-6 (gnd)
          pins 7-8 (5vres marked on board, but no pins connected)
          pins 9-10 (gnd marked on board, but pin 10 is N/C)
          pins 11-12 (reg_12v)= 11.82v
          pin 13 (vblon)= 3.3v
          pin 14 (dim)= 2.278v
          pin 15 (lamp_det marked on board, but pin is N/C)

          led driver board:
          cn1 (14 pins)
          pins 1-5 (vddb)= 24.69v
          pins 6-10 (blgnd)
          pin 11 (det)= 0v
          pin 12 (vblon)= 3.3v
          pin 13 (N/C)
          pin 14 (e_pwm)= 2.278v

          cn2 (12 pins)
          pins 1-5 (vddb)= 24.69v
          pins 6-10 (blgnd)
          pins 11-12 (N/C)

          cn3 (12 pins to led strips, only uses six wires)
          pin 1 (1anode)= 24.41v
          pins 2-3 (N/C)
          pin 4 (2cathode)= didn't measure this pin
          pin 5 (3anode)= 24.41v
          pins 6-7 (N/C)
          pin 8 (4cathode)= didn't measure this pin
          pin 9 (5anode)= 24.41v
          pin 10-11 (N/C)
          pin 12 (6cathode)= didn't measure this pin
          ================================================== ========

          what i have done so far:

          only problem i could find on original led driver board was that pin 5 (3anode) did not have any voltage on it.
          fuse f2 was blown.

          disassemble panel and check each individual led strip (12 of them) using a hp laptop psu with output of 19.28 volts.
          all led on each string lit completely.

          bought this kit from shopjimmy:
          https://www.shopjimmy.com/vizio-e650...air-parts-kit/

          fed a full 3.3v to ps_on (with wire to main disconnected, of course) because i thought 2.368v might be too low
          (made no difference).

          so, long story long ;-) tv acts same as original boards. power comes on and backlight flashes once, then turns off.
          flashlight shows image (says "no signal" after displaying vizio logo) and have audio, but nada from backlights.
          initial voltage on led driver board cn3 (pins 1,5,and 9) is 84v then dropping and holding at 24v.

          the only signal i see that might be a problem is the DET signal, but i don't know. i'm a noob on these led backlit
          tv's, so i would appreciate some help from the Wise Ones here on the forum. Thanks! James

          Comment

          • Lee M.
            Member
            • Nov 2021
            • 35
            • United States

            #6
            Re: Vizio V755-J04 no backlight

            The post above is another Vizio with the same symptoms as mine. He checked the BL led's and they were all good. "disassemble panel and check each individual led strip (12 of them) using a hp laptop psu with output of 19.28 volts.
            all led on each string lit completely." So I'm assuming the problem was with the driver board, but the OP never posted what the fix turned out to be.

            Comment

            • diif
              Badcaps Legend
              • Feb 2014
              • 6978
              • England

              #7
              Re: Vizio V755-J04 no backlight

              Originally posted by Lee M.
              If there is one or more shorted LED's the amp draw would be high and the protection circuit would shut down the BL's. But if I disconnect the BL's so there is no load it does the same exact thing, 90V for 1/2 sec and then nothing. It seems like I remember testing other BL driver boards and when I disconnected the BL's the voltage on the connector pins would stay up and not drop to zero with no load like this one is doing. That is how I knew the BL's were bad and not the driver board. Since this one is acting the same regardless if the BL's are connected or not has me wondering if the driver board might be bad?
              You're aware LEDs can fail open too ?

              Comment

              • Lee M.
                Member
                • Nov 2021
                • 35
                • United States

                #8
                Re: Vizio V755-J04 no backlight

                Right I know led's can fail open, but I have not seen a TV with a protection circuit that turns off the voltage due to an open circuit. The few sets I've worked on still had voltage on the BL pins with the BL's disconnected. Since this is a 75" TV I was hoping to avoid taking the panel apart risking breaking it only to find all the led's are good like the poster above did with another Vizio.

                Comment

                • dskall
                  Badcaps Legend
                  • Oct 2016
                  • 2905
                  • usa

                  #9
                  Re: Vizio V755-J04 no backlight

                  That's why they only go to a certain voltage and then shut down. Also, lighting 12 leds with 19v is not a proper check. In fact, most backlight testers can't load leds like the tv does.
                  I assume no responsibility for any stupid suggestions I might post.

                  Comment

                  • nomoresonys
                    Badcaps Legend
                    • Jan 2013
                    • 12097
                    • U.S.

                    #10
                    Re: Vizio V755-J04 no backlight

                    from what I can tell, the only problem I see with your voltages is the ac-det, which should probably be about 3.3 volts.

                    Comment

                    • nomoresonys
                      Badcaps Legend
                      • Jan 2013
                      • 12097
                      • U.S.

                      #11
                      Re: Vizio V755-J04 no backlight

                      no ac det usually means a problem with power board.

                      Comment

                      • Storyteller12
                        Badcaps Veteran
                        • Jun 2020
                        • 624
                        • USA

                        #12
                        Re: Vizio V755-J04 no backlight

                        Please post pictures of the boards. Second post asked but you never uploaded them.

                        Comment

                        • Lee M.
                          Member
                          • Nov 2021
                          • 35
                          • United States

                          #13
                          Re: Vizio V755-J04 no backlight

                          Here's some pics, sorry for the delay.
                          Attached Files

                          Comment

                          • dskall
                            Badcaps Legend
                            • Oct 2016
                            • 2905
                            • usa

                            #14
                            Re: Vizio V755-J04 no backlight

                            Replace your backlights.
                            I assume no responsibility for any stupid suggestions I might post.

                            Comment

                            • nomoresonys
                              Badcaps Legend
                              • Jan 2013
                              • 12097
                              • U.S.

                              #15
                              Re: Vizio V755-J04 no backlight

                              Originally posted by Lee M.
                              Right I know led's can fail open, but I have not seen a TV with a protection circuit that turns off the voltage due to an open circuit. The few sets I've worked on still had voltage on the BL pins with the BL's disconnected. Since this is a 75" TV I was hoping to avoid taking the panel apart risking breaking it only to find all the led's are good like the poster above did with another Vizio.
                              get a backlight tester, they're not perfect but they are very useful to get a clue of whats going on, around 20 bucks on amazon, a small price to pay compared to a broken screen or the total teardown required for most backlight replacement jobs, which has to be done anyway if that is the problem.

                              Comment

                              • nomoresonys
                                Badcaps Legend
                                • Jan 2013
                                • 12097
                                • U.S.

                                #16
                                Re: Vizio V755-J04 no backlight

                                Ideally you want one that gives both voltage and current readings, example there: https://www.amazon.com/HELYZQ-0-320V...3D%3D&sr=8-162

                                Comment

                                • nomoresonys
                                  Badcaps Legend
                                  • Jan 2013
                                  • 12097
                                  • U.S.

                                  #17
                                  Re: Vizio V755-J04 no backlight

                                  notice that one goes to 320 volts, some of the others only go to 230 or so.

                                  Comment

                                  • diif
                                    Badcaps Legend
                                    • Feb 2014
                                    • 6978
                                    • England

                                    #18
                                    Re: Vizio V755-J04 no backlight

                                    Maximum current is only 35mA with that tester, that's more of a gentle tickle.

                                    One that tests up to 150mA https://www.aliexpress.com/item/1005002498419259.html

                                    Comment

                                    • nomoresonys
                                      Badcaps Legend
                                      • Jan 2013
                                      • 12097
                                      • U.S.

                                      #19
                                      Re: Vizio V755-J04 no backlight

                                      its all about how much you want to spend, I doubt the op wants to go into the tv repair business or I would have suggested something better than both of those and I doubt he would want to wait 2 to 6 weeks to get it.
                                      Last edited by nomoresonys; 10-08-2022, 08:17 AM.

                                      Comment

                                      • diif
                                        Badcaps Legend
                                        • Feb 2014
                                        • 6978
                                        • England

                                        #20
                                        Re: Vizio V755-J04 no backlight

                                        Which one do you recommend that's better than both

                                        Comment

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